Fiber-ring delay line for high-resolution intersatellite ranging

There is a growing need for accurate, high-resolution intersatellite ranging, for instance for gravitational mapping, which has led to extensive research on optical methods that can augment or replace existing spaceborne microwave techniques. In this letter, we outline a top-level design concept for intersatellite ranging based on measurements using a homodyne Mach-Zehnder interferometer housed on one satellite. The phase degradation in the reference arm of the interferometer on the local satellite is maintained at a minimal level to yield useful interference with the measuring arm that traverses hundreds of kilometers to the remote satellite and back. In this preliminary study, the feasibility of the concept in terms of link budget and noise level is validated. Ranging resolution is expected to be similar to the current heterodyne state-of-the-art.